Respiratory and circulatory diseases cause significant economic losses to the commercial meat industry. For example, bovine respiratory disease (BRD) has been estimated to account for 65% to 79% of the sickness and up to 72% of the deaths of feedlot cattle. BRD includes several more specific forms of respiratory diseases, including upper respiratory tract infections, diphtheria and pneumonia. Both viral and bacterial agents can cause BRD. These agents can be difficult or impossible to control. Cattle have natural defense systems for combating these agents, but these defense systems often are compromised by stress, such as stress associated with normal cattle management.
A significant percentage of livestock experience respiratory or circulatory disease at one or more times during their life. In most cases, the animals recover from the disease, but experience some degree of permanent internal damage. For example, studies on carcasses have shown that about one third to about one half of all cattle have lung lesions at slaughter that are the result of past respiratory disease.
To control respiratory diseases, such as BRD, many livestock managers actively diagnose and treat outbreaks. When detected, infected livestock typically are quarantined and treated with antibiotic and/or antiviral medications. These remedial efforts can be expensive and often fail to cure the disease. The success of treatment depends largely on the respiratory heath of the animal prior to onset of the disease. It has been shown, for example, that animals with significantly damaged respiratory systems from past respiratory disease are much less likely to respond well to treatment than animals with relatively undamaged respiratory systems.
In addition to affecting how animals respond to treatment, respiratory damage from past respiratory disease can adversely affect an animal's performance at the feedlot. For example, feedlot cattle with greater amounts of respiratory damage have been shown to gain less weight than feedlot cattle with lesser amounts of respiratory damage. In addition, the meat derived from cattle with greater amounts of respiratory damage often is of lower quality than the meat derived from cattle with lesser amounts of respiratory damage. Finally, the presence of respiratory damage from past respiratory disease may cause meat to fail to qualify as kosher, thereby decreasing its market value.